The present invention relates to a pin of synthetic material, especially polyamide, for a pin lane, and also including so-called bowling pins. The pin includes a core that is provided with pockets and/or cells during production by the addition of an expansion agent. The core is enveloped by a sheathing that is fixedly secured thereto; the sheathing is of solid wall construction and is essentially free of pockets and/or cells. The pin can, especially in the region of its base, be provided with reinforcements, carrying means, fittings, or the like, which, however, are not part of the subject matter of the present invention.
The present invention also relates to methods of producing such a pin.
The phrase "of solid wall construction" is used within the context of the present invention to refer to a homogeneous construction that is essentially free of hollow spaces; thus, the plastic layer constructed in this manner has no or essentially no gas pockets.
It is well known that a pin experiences a relatively high mechanical stress when it is struck by a ball.
The aforementioned construction of a pin of synthetic material is expedient because its core is lightweight due to the presence of the gas pockets, and its sheathing, with the solid wall construction thereof, is a suitable shell-like strength-carrying member.
The bonding between the aforementioned core and the sheathing of solid wall construction is of great significance for the endurance strength of the pin. The adhesive surface brought about by the application of the sheathing to the core assures a good bonding when the surfaces that are to be connected to one another are smooth and as little roughened or full of fissures as possible.
It is therefore an object of the present invention for pins of the aforementioned general type, where the separately produced core is provided with the aforementioned sheathing by having the latter sprayed, etc., thereabout, to provide an increased and improved bonding between the core and the sheathing.